Tissue Contact Interface

ABSTRACT

An apparatus, system, and method for closing an opening through a surface of a tissue site is described. The apparatus includes an apposition layer adapted to be positioned over the opening. The apposition layer is formed from a material having a firmness factor, and has a plurality of holes extending through the apposition layer. The holes form a void space and have a perforation shape factor and a strut angle configured to collapse the apposition layer in a first direction relative to a second direction. A sheet having a plurality of perforations is configured to surround the apposition layer, the sheet having a plurality of perforations. The apposition layer generates a closing force in the first direction that is substantially parallel to the surface of the tissue site to close the opening in response to application of a negative pressure.

RELATED APPLICATION

This application claims the benefit, under 35 U.S.C. § 119(e), of thefiling of U.S. Provisional Patent Application Ser. No. 62/516,540,entitled “TISSUE CONTACT INTERFACE,” filed Jun. 7, 2017; U.S.Provisional Patent Application Ser. No. 62/516,550, entitled “COMPOSITEDRESSINGS FOR IMPROVED GRANULATION AND REDUCED MACERATION WITHNEGATIVE-PRESSURE TREATMENT” filed Jun. 7, 2017; and U.S. ProvisionalPatent Application Ser. No. 62/516,566, entitled “COMPOSITE DRESSINGSFOR IMPROVED GRANULATION AND REDUCED MACERATION WITH NEGATIVE-PRESSURETREATMENT” filed Jun. 7, 2017, each of which is incorporated herein byreference for all purposes.

TECHNICAL FIELD

The invention set forth in the appended claims relates generally totissue treatment systems and more particularly, but without limitation,to a dressing having a contracting layer for assisting in closure oflinear tissue sites.

BACKGROUND

Clinical studies and practice have shown that reducing pressure inproximity to a tissue site can augment and accelerate growth of newtissue at the tissue site. The applications of this phenomenon arenumerous, but it has proven particularly advantageous for treatingwounds. Regardless of the etiology of a wound, whether trauma, surgery,or another cause, proper care of the wound is important to the outcome.Treatment of wounds or other tissue with negative pressure may becommonly referred to as “negative-pressure therapy,” but is also knownby other names, including “negative-pressure wound therapy,”“reduced-pressure therapy,” “vacuum therapy,” “vacuum-assisted closure,”and “topical negative-pressure,” for example. Negative-pres sure therapymay provide a number of benefits, including migration of epithelial andsubcutaneous tissues, improved blood flow, and micro-deformation oftissue at a wound site. Together, these benefits can increasedevelopment of granulation tissue and reduce healing times.

While the clinical benefits of negative-pressure therapy are widelyknown, improvements to therapy systems, components, and processes mayfurther benefit healthcare providers and patients.

BRIEF SUMMARY

New and useful systems, apparatuses, and methods for closing an openingthrough a surface of a tissue site are set forth in the appended claims.Illustrative embodiments are also provided to enable a person skilled inthe art to make and use the claimed subject matter. For example, asystem for closing an opening through a surface of a tissue site isdescribed. The system can include an apposition layer adapted to bepositioned over the opening. The apposition layer may be formed from amaterial having a firmness factor, and have a plurality of holesextending through the apposition layer. The holes can form a void spaceand have a perforation shape factor and a strut angle configured tocollapse the apposition layer in a first direction relative to a seconddirection. A first layer can be adapted to be positioned below theapposition layer, the first layer having at least one perforation. Asecond layer can be adapted to be positioned above the apposition layer,the second layer having at least one perforation. The system can alsoinclude a dressing adapted to cover the apposition layer to form asealed space, and a negative-pressure source adapted to be fluidlycoupled to the sealed space to provide negative pressure to the sealedspace. The apposition layer can generate a closing force in the firstdirection that is substantially parallel to the surface of the tissuesite to close the opening in response to application of a negativepressure.

Alternatively, other example embodiments include an apparatus forclosing an opening through a surface of a tissue site. The apparatus caninclude a contracting layer adapted to be positioned over the opening.The contracting layer is formed from a material having a firmnessfactor, and has a plurality of holes extending through the contractinglayer. The holes form a void space and have a perforation shape factorand a strut angle configured to collapse the apposition layer in a firstdirection relative to a second direction. The apparatus may furtherinclude a lower layer adapted to be positioned below the contractinglayer, the lower layer having at least one perforation, and an upperlayer adapted to be positioned above the contracting layer, the upperlayer having at least one perforation. The contracting layer generates aclosing force in the first direction that is substantially parallel tothe surface of the tissue site to close the opening in response toapplication of a negative pressure.

A method for closing an opening through a surface of a tissue site isalso described. An apposition layer can be encapsulated in a sheethaving an upper layer above the apposition layer and a lower layer belowthe apposition layer, the sheet having at least one perforation in theupper layer and at least one perforation in the lower layer. Theapposition layer can be positioned over the opening. The appositionlayer may be adapted to be positioned adjacent the opening and formedfrom a material having a firmness factor and a plurality of holesextending through the apposition layer to form a void space. The holeshave a perforation shape factor and a strut angle causing the appositionlayer to collapse in a direction substantially perpendicular to theopening. The apposition layer can be collapsed parallel to the surfaceof the tissue site to generate a closing force.

Objectives, advantages, and a preferred mode of making and using theclaimed subject matter may be understood best by reference to theaccompanying drawings in conjunction with the following detaileddescription of illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view with a portion shown in elevation of anillustrative example of a system for treating a tissue site having adressing deployed at the tissue site;

FIG. 2 is a plan view of a base layer of the dressing of FIG. 1,illustrating additional details that may be associated with someembodiments;

FIG. 3 is an exploded view of the dressing of FIG. 1, illustratingadditional details that may be associated with some embodiments;

FIG. 4 is detail view of a portion of the dressing of FIG. 1,illustrating additional details that may be associated with someembodiments;

FIG. 5 is a plan view of an apposition layer of the system of FIG. 1,illustrating additional details that may be associated with someembodiments;

FIG. 6A is a plan view of the apposition layer of FIG. 5 in a firstposition, illustrating additional details that may be associated withsome embodiments;

FIG. 6B is a detail view of a portion of the holes of the appositionlayer of FIG. 6A, illustrating additional details that may be associatedwith some embodiments;

FIG. 6C is a plan view of the apposition layer of FIG. 6A in a secondposition, illustrating additional details that may be associated withsome embodiments;

FIG. 7 is a schematic view of a hole of the apposition layer of FIG. 6Ahaving a perforation shape factor, illustrating additional details thatmay be associated with some embodiments;

FIG. 8 is a schematic view of a hole of the apposition layer of FIG. 6Ahaving another perforation shape factor, illustrating additional detailsthat may be associated with some embodiments;

FIG. 9 is a schematic view of a hole of the apposition layer of FIG. 6Ahaving another perforation shape factor, illustrating additional detailsthat may be associated with some embodiments;

FIG. 10 is an exploded view of the apposition layer and the dressing ofFIG. 1 disposed over the tissue site, illustrating additional detailsthat may be associated with some embodiments;

FIG. 11 is a perspective view of the apposition layer and the dressingdisposed over the tissue site in a first position, illustratingadditional details that may be associated with some embodiments;

FIG. 12 is a perspective view of the apposition layer and the dressingdisposed over the tissue site in a second position, illustratingadditional details that may be associated with some embodiments;

FIG. 13A is a perspective section view of another apposition layer thatmay be used with the negative-pressure therapy system of FIG. 1,illustrating additional details that may be associated with someembodiments;

FIG. 13B is a sectional view the apposition layer of FIG. 13A in a firstposition taken along line 13B-13B, illustrating additional details thatmay be associated with some embodiments;

FIG. 13C is a sectional view of the apposition layer of FIG. 13A in asecond position, illustrating additional details that may be associatedwith some embodiments;

FIG. 14 is a perspective view of a another apposition layer that may beused with the negative-pressure therapy system of FIG. 1, illustratingadditional details that may be associated with some embodiments; and

FIG. 15 is a perspective view of another apposition layer that may beused with the negative-pressure therapy system of FIG. 1, illustratingadditional details that may be associated with some embodiments.

DESCRIPTION OF EXAMPLE EMBODIMENTS

The following description of example embodiments provides informationthat enables a person skilled in the art to make and use the subjectmatter set forth in the appended claims, but may omit certain detailsalready well-known in the art. The following detailed description is,therefore, to be taken as illustrative and not limiting.

The example embodiments may also be described herein with reference tospatial relationships between various elements or to the spatialorientation of various elements depicted in the attached drawings. Ingeneral, such relationships or orientation assume a frame of referenceconsistent with or relative to a patient in a position to receivetreatment. However, as should be recognized by those skilled in the art,this frame of reference is merely a descriptive expedient rather than astrict prescription.

Referring to the drawings, FIG. 1 depicts an illustrative embodiment ofa system 102 for treating a tissue site 104 of a patient. The tissuesite 104 may extend through or otherwise involve an epidermis 106, adermis 108, and a subcutaneous tissue 110. The tissue site 104 may be asub-surface tissue site as depicted in FIG. 1 that may extend below atissue surface 105 of the epidermis 106. Further, the tissue site 104may predominantly reside on the tissue surface 105 of the epidermis 106,such as, for example, an incision. Regardless of the positioning of thesystem 102 or the type of tissue site 104, the system 102 may providetherapy to, for example, the epidermis 106, the dermis 108, and thesubcutaneous tissue 110. The system 102 may also be used withoutlimitation at other tissue sites.

The tissue site 104 may be the bodily tissue of any human, animal, orother organism. Treatment of the tissue site 104 may include the removalof fluids, such as exudate or ascites. The term “tissue site” in thiscontext may also broadly refer to a wound or a defect located on orwithin tissue, including but not limited to, bone tissue, adiposetissue, muscle tissue, neural tissue, dermal tissue, vascular tissue,connective tissue, cartilage, tendons, ligaments, or any other tissue. Awound may include chronic, acute, traumatic, subacute, and dehiscedwounds, partial-thickness burns, ulcers (such as diabetic, pressure, orvenous insufficiency ulcers), flaps, and grafts, for example. The term“tissue site” may also refer to areas of any tissue that are notnecessarily wounded or defective, but are instead areas in which it maybe desirable to add or promote the growth of additional tissue. Forexample, negative pressure may be used at a tissue site to growadditional tissue that may be harvested and transplanted to a tissuesite at another location.

A tissue site may also refer to a linear tissue site. A linear tissuesite may generally refer to a tissue site having an elongated shape,such as an incision having a length substantially greater than itswidth. An incision may have edges that may be substantially parallel,particularly if the incision is caused by a scalpel, knife, razor, orother sharp blade. Other examples of a linear tissue site may include alaceration, a puncture, or other separation of tissue, which may havebeen caused by trauma, surgery, or degeneration. In some embodiments, alinear tissue site may also be an incision in an organ adjacent afistula. In some embodiments, a linear tissue site may be an incision orpuncture in otherwise healthy tissue that extends up to 40 cm or more inlength. In some embodiments, a linear tissue site may also vary indepth. For example, an incision may have a depth that extends up to 15cm or more or may be subcutaneous depending on the type of tissue andthe cause of the incision.

The system 102 may include a tissue interface, such as an interfacemanifold 120, a contracting layer, such as an apposition layer 146, adressing 124, and a negative-pressure source 128. The interface manifold120 may be adapted to be positioned proximate to or adjacent to thetissue site 104, such as, for example, by cutting or otherwise shapingthe interface manifold 120 to fit the tissue site 104. In otherembodiments, the interface manifold 120 may be omitted. The appositionlayer 146 may have a thickness 126 and be enclosed by a sheet 147 andpositioned over the interface manifold 120 and the tissue site 104. Andthe dressing 124 may be positioned over the apposition layer 146 and theinterface manifold 120. The negative-pressure source 128 can be coupledto the dressing through a conduit interface 148.

The dressing 124 may include a base layer 132, an adhesive layer 136, afluid management assembly 144, and a cover, such as a sealing member140. The base layer 132 may be positioned over the apposition layer 146,the interface manifold 120, and the tissue surface 105 of the epidermis106. The base layer 132 may include a plurality of apertures 160extending through the base layer 132. The fluid management assembly 144may be positioned over the base layer 132. The sealing member 140 can bepositioned over the fluid management assembly 144. In some embodiments,a periphery of the sealing member 140 may be sealed to a periphery ofthe base layer 132 by the adhesive layer 136 to form an enclosure 172containing the fluid management assembly 144. Components of the dressing124 may be added or removed to suit particular applications.

The conduit interface 148 may be coupled to the dressing 124. Theconduit interface may be coupled to the sealing member 140 so that theconduit interface 148 fluidly communicates with the enclosure 172. Theconduit interface 148 may include an odor filter 194 and a firsthydrophobic filter 195. The conduit interface 148 can be fluidly coupledto the negative-pressure source 128 through a conduit 196 having aninternal lumen 197. In some embodiments, the conduit 196 may be coupledto the negative-pressure source through a coupling 198 of thenegative-pressure source 128. A secondary hydrophobic filter 199 may bedisposed in the fluid path through the coupling 198. A liquid trap 192may be disposed in the fluid path between the conduit interface 148 andthe negative-pressure source 128. For example, the conduit 196 maycomprise two or more conduits. A first conduit fluidly coupled betweenthe conduit interface 148 and the liquid trap 192, and a second conduitfluidly coupled between the liquid trap 192 and the negative-pressuresource 128.

In general, components of the system 102 may be coupled directly orindirectly. For example, the negative-pressure source 128 may bedirectly coupled to the liquid trap 192 and indirectly coupled to thedressing 124 through the liquid trap 192. Components may be fluidlycoupled to each other to provide a path for transferring fluids (i.e.,liquid and/or gas) between the components.

In some embodiments, components may be fluidly coupled through a tube,such as the conduit 196. A “conduit” or “tube,” as used herein, broadlyrefers to a tube, pipe, hose, conduit, or other structure with one ormore lumina adapted to convey a fluid between two ends. Typically, atube is an elongated, cylindrical structure with some flexibility, butthe geometry and rigidity may vary. In some embodiments, components mayadditionally or alternatively be coupled by virtue of physicalproximity, being integral to a single structure, or being formed fromthe same piece of material. Coupling may also include mechanical,thermal, electrical, or chemical coupling (such as a chemical bond) insome contexts.

In operation, a tissue interface, such as an interface manifold 120, maybe placed within, over, on, or otherwise proximate to a tissue site. Acover, such as the sealing member 140, may be placed over a tissueinterface and sealed to tissue near a tissue site. For example, theinterface manifold 120 may be placed over the tissue site 104, and thesealing member 140 may be sealed to undamaged epidermis peripheral tothe tissue site 104, for example, to the tissue surface 105. Thus, acover can provide a sealed therapeutic environment or a sealed space 174proximate to the tissue site 104 that is substantially isolated from theexternal environment, and the negative-pressure source 128 may reducethe pressure in the sealed space 174.

The fluid mechanics of using a negative-pressure source to reducepressure in another component or location, such as within a sealedtherapeutic environment, can be mathematically complex. However, thebasic principles of fluid mechanics applicable to negative-pressuretherapy are generally well-known to those skilled in the art, and theprocess of reducing pressure may be described illustratively herein as“delivering,” “distributing,” or “generating” negative pressure, forexample.

In general, exudates and other fluids flow toward lower pressure along afluid path. Thus, the term “downstream” typically refers to a positionin a fluid path relatively closer to a negative-pressure source.Conversely, the term “upstream” refers to a position relatively furtheraway from a negative-pressure source. Similarly, it may be convenient todescribe certain features in terms of fluid “inlet” or “outlet” in sucha frame of reference. This orientation is generally presumed forpurposes of describing various features and components ofnegative-pressure therapy systems herein. However, the fluid path mayalso be reversed in some applications (such as by substituting apositive-pressure source for a negative-pressure source) and thisdescriptive convention should not be construed as a limiting convention.

“Negative pressure” generally refers to a pressure less than a localambient pressure, such as the ambient pressure in a local environmentexternal to a sealed therapeutic environment provided by the dressing124. In many cases, the local ambient pressure may also be theatmospheric pressure at which a tissue site is located. Alternatively,the pressure may be less than a hydrostatic pressure associated withtissue at the tissue site. Unless otherwise indicated, values ofpressure stated herein are gauge pressures. Similarly, references toincreases in negative pressure typically refer to a decrease in absolutepressure, while decreases in negative pressure typically refer to anincrease in absolute pressure. While the amount and nature of negativepressure applied to a tissue site may vary according to therapeuticrequirements, the pressure is generally a low vacuum, also commonlyreferred to as a rough vacuum, between −5 mm Hg (−667 Pa) and −500 mm Hg(−66.7 kPa). Common therapeutic ranges are between −75 mm Hg (−9.9 kPa)and −300 mm Hg (−39.9 kPa).

A negative-pressure supply, such as the negative-pressure source 128,may be a reservoir of air at a negative pressure, or may be a manual orelectrically-powered device that can reduce the pressure in a sealedvolume, such as a vacuum pump, a suction pump, a wall suction portavailable at many healthcare facilities, or a micro-pump, for example. Anegative-pressure supply may be housed within or used in conjunctionwith other components, such as sensors, processing units, alarmindicators, memory, databases, software, display devices, or userinterfaces that further facilitate therapy. For example, in someembodiments, the negative-pressure source 128 may be combined withcontrollers and other components into a therapy unit. Anegative-pressure supply may also have one or more supply portsconfigured to facilitate coupling and de-coupling the negative-pressuresupply to one or more distribution components.

The interface manifold 120 can be generally adapted to contact a tissuesite. The interface manifold 120 may be partially or fully in contactwith the tissue site. If the tissue site is a wound, for example, theinterface manifold 120 may partially or completely fill the wound, ormay be placed over the wound. The interface manifold 120 may take manyforms, and may have many sizes, shapes, or thicknesses depending on avariety of factors, such as the type of treatment being implemented orthe nature and size of a tissue site. For example, the size and shape ofthe interface manifold 120 may be adapted to the contours of deep andirregular shaped tissue sites. Moreover, any or all of the surfaces ofthe interface manifold 120 may have projections or an uneven, course, orjagged profile that can induce strains and stresses on a tissue site,which can promote granulation at the tissue site.

In some illustrative embodiments, the pathways of a manifold may beinterconnected to improve distribution or collection of fluids across atissue site. In some illustrative embodiments, a manifold may be aporous foam material having interconnected cells or pores. For example,cellular foam, open-cell foam, reticulated foam, porous tissuecollections, and other porous material such as gauze or felted matgenerally include pores, edges, and/or walls adapted to forminterconnected fluid channels. Liquids, gels, and other foams may alsoinclude or be cured to include apertures and fluid pathways. In someembodiments, a manifold may additionally or alternatively compriseprojections that form interconnected fluid pathways. For example, amanifold may be molded to provide surface projections that defineinterconnected fluid pathways.

The average pore size of a foam may vary according to needs of aprescribed therapy. For example, in some embodiments, the interfacemanifold 120 may be a foam having pore sizes in a range of 400-600microns. The tensile strength of the interface manifold 120 may alsovary according to needs of a prescribed therapy. For example, thetensile strength of a foam may be increased for instillation of topicaltreatment solutions. In one non-limiting example, the interface manifold120 may be an open-cell, reticulated polyurethane foam such asGranuFoam® dressing or VeraFlo® foam, both available from KineticConcepts, Inc. of San Antonio, Tex.

The interface manifold 120 may be either hydrophobic or hydrophilic. Inan example in which the interface manifold 120 may be hydrophilic, theinterface manifold 120 may also wick fluid away from a tissue site,while continuing to distribute negative pressure to the tissue site. Thewicking properties of the interface manifold 120 may draw fluid awayfrom a tissue site by capillary flow or other wicking mechanisms. Anexample of a hydrophilic foam is a polyvinyl alcohol, open-cell foamsuch as V.A.C. WhiteFoam® dressing available from Kinetic Concepts, Inc.of San Antonio, Tex. Other hydrophilic foams may include those made frompolyether. Other foams that may exhibit hydrophilic characteristicsinclude hydrophobic foams that have been treated or coated to providehydrophilicity.

The interface manifold 120 may further promote granulation at a tissuesite when pressure within the sealed therapeutic environment is reduced.For example, any or all of the surfaces of the interface manifold 120may have an uneven, coarse, or jagged profile that can inducemicrostrains and stresses at a tissue site if negative pressure isapplied through the interface manifold 120.

In some embodiments, the interface manifold 120 may be constructed frombioresorbable materials. Suitable bioresorbable materials may include,without limitation, a polymeric blend of polylactic acid (PLA) andpolyglycolic acid (PGA). The polymeric blend may also include withoutlimitation polycarbonates, polyfumarates, and capralactones. Theinterface manifold 120 may further serve as a scaffold for newcell-growth, or a scaffold material may be used in conjunction with theinterface manifold 120 to promote cell-growth. A scaffold is generally asubstance or structure used to enhance or promote the growth of cells orformation of tissue, such as a three-dimensional porous structure thatprovides a template for cell growth. Illustrative examples of scaffoldmaterials include calcium phosphate, collagen, PLA/PGA, coral hydroxyapatites, carbonates, or processed allograft materials.

The sealing member 140 may be formed from a material that allows for afluid seal. A fluid seal may be a seal adequate to maintain negativepressure at a desired site given the particular negative pressure sourceor system involved. The sealing member 140 may comprise, for example,one or more of the following materials: hydrophilic polyurethane;cellulosics; hydrophilic polyamides; polyvinyl alcohol; polyvinylpyrrolidone; hydrophilic acrylics; hydrophilic silicone elastomers; anINSPIRE 2301 material from Expopack Advanced Coatings of Wrexham, UnitedKingdom having, for example, an MVTR (inverted cup technique) of 14400g/m²/24 hours and a thickness of about 30 microns; a thin, uncoatedpolymer drape; natural rubbers; polyisoprene; styrene butadiene rubber;chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber;ethylene propylene rubber; ethylene propylene diene monomer;chlorosulfonated polyethylene; polysulfide rubber; polyurethane (PU);EVA film; co-polyester; silicones; a silicone drape; a 3M Tegaderm®drape; a polyurethane (PU) drape such as one available from AveryDennison Corporation of Pasadena, Calif.; polyether block polyamidecopolymer (PEBAX), for example, from Arkema, France; Expopack 2327; orother appropriate material.

The sealing member 140 may be vapor permeable and liquid impermeable,thereby allowing vapor and inhibiting liquids from exiting the sealedspace 174 provided by the dressing 124. In some embodiments, the sealingmember 140 may be a flexible, breathable film, membrane, or sheet havinga high MVTR of, for example, at least about 300 g/m² per 24 hours. Inother embodiments, a low or no vapor transfer drape may be used. Thesealing member 140 may comprise a range of medically suitable filmshaving a thickness between about 25 microns (μm) to about 50 microns(μm).

An attachment device, such as the adhesive layer 136, may be used toattach the sealing member 140 to an attachment surface, such asundamaged epidermis, a gasket, another cover, or the base layer 132. Theattachment device may take many forms. For example, an attachment devicemay be a medically-acceptable, pressure-sensitive adhesive that extendsabout a periphery, a portion, or an entire sealing member. In someembodiments, for example, some or all of the sealing member 140 may becoated with an acrylic adhesive having a coating weight between 25-65grams per square meter (g.s.m.). Thicker adhesives, or combinations ofadhesives, may be applied in some embodiments to improve the seal andreduce leaks. Other example embodiments of an attachment device mayinclude a double-sided tape, paste, hydrocolloid, hydrogel, siliconegel, or organogel.

In some embodiments, the adhesive layer 136 may be deformable orflowable. For example, the adhesive layer 136 may comprise an acrylicadhesive, rubber adhesive, high-tack silicone adhesive, polyurethane, orother adhesive substance. In some embodiments, the adhesive layer 136may be a pressure-sensitive adhesive comprising an acrylic adhesive. Theadhesive layer 136 may be continuous or discontinuous. Discontinuitiesin the adhesive layer 136 may be provided by the apertures (not shown)in the adhesive layer 136. The apertures in the adhesive layer 136 maybe formed after application of the adhesive layer 136 or by coating theadhesive layer 136 in patterns on a carrier layer, such as, for example,a side of the sealing member 140 adapted to face the tissue surface 105of the epidermis 106. The apertures in the adhesive layer 136 may alsobe sized to enhance the Moisture Vapor Transfer Rate (MVTR) of thedressing 124, described further herein.

A fluid storage device, such as the fluid management assembly 144, maybe an example of a device to configured to store liquids in the dressing124. The fluid management assembly 144 may include a first dressingwicking layer 176, a second dressing wicking layer 180, and an absorbentlayer 184. The first dressing wicking layer 176 is positioned adjacentto the base layer 132, and the absorbent layer 184 is positionedadjacent the first dressing wicking layer 176. The second dressingwicking layer 180 may be positioned over the absorbent layer 184 andperipheries of the first dressing wicking layer 176 and the seconddressing wicking layer 180 may be coupled to each other to form awicking layer enclosure 188 containing the absorbent layer 184. In someembodiments, an anti-microbial layer 190 may be disposed in the wickinglayer enclosure 188 between the first dressing wicking layer 176 and theabsorbent layer 184. In some embodiments, the wicking layer enclosure188 may surround or otherwise encapsulate the absorbent layer 184between the first dressing wicking layer 176 and the second dressingwicking layer 180.

In some embodiments, the absorbent layer 184 may be in fluidcommunication with the first dressing wicking layer 176 and the seconddressing wicking layer 180. The first dressing wicking layer 176 mayhave a grain structure adapted to wick fluid along a surface of thefirst dressing wicking layer 176. Similarly, the second dressing wickinglayer 180 may have a grain structure adapted to wick fluid along asurface of the second dressing wicking layer 180. For example, the firstdressing wicking layer 176 and the second dressing wicking layer 180 maywick or otherwise transport fluid in a lateral direction along thesurfaces of the first dressing wicking layer 176 and the second dressingwicking layer 180, respectively. The surface of the first dressingwicking layer 176 may be normal relative to the thickness of the firstdressing wicking layer 176, and the surface of the second dressingwicking layer 180 may be normal relative to the thickness of the seconddressing wicking layer 180. The wicking of fluid along the firstdressing wicking layer 176 and the second dressing wicking layer 180 mayenhance the distribution of the fluid over a surface area of theabsorbent layer 184, which may increase absorbent efficiency and resistfluid blockages. Fluid blockages may be caused by, for example, fluidpooling in a particular location in the absorbent layer 184 rather thanbeing distributed more uniformly across the absorbent layer 184. Thelaminate combination of the first dressing wicking layer 176, the seconddressing wicking layer 180, and the absorbent layer 184 may be adaptedas described above to maintain an open structure, resistant to blockage,capable of maintaining fluid communication with, for example, the tissuesite 104.

The fluid management assembly 144 may include, without limitation, anynumber of wicking layers and absorbent layers as desired for treating aparticular tissue site. For example, the absorbent layer 184 may be aplurality of absorbent layers 184 positioned in fluid communicationbetween the first dressing wicking layer 176 and the second dressingwicking layer 180. Further, in some embodiments, at least oneintermediate wicking layer may be disposed in fluid communicationbetween the plurality of absorbent layers 184. Similar to the absorbentlayer 184, the plurality of absorbent layers 184 and the at least oneintermediate wicking layer may be positioned within the wicking layerenclosure 188. In some embodiments, the absorbent layer 184 may bedisposed between the sealing member 140 and the interface manifold 120,and the first dressing wicking layer 176 and the second dressing wickinglayer 180 may be omitted.

In some embodiments, the absorbent layer 184 may be a hydrophilicmaterial adapted to absorb fluid from, for example, the tissue site 104.Materials suitable for the absorbent layer 184 may include, withoutlimitation, super absorbent polymers and similar absorbent materials;Luquafleece® material; TEXSUS FP2326; BASF 402C; Technical Absorbents2317, available from Technical Absorbents, Ltd. of Lincolnshire, UnitedKingdom; sodium polyacrylate super absorbers; cellulosics (carboxymethyl cellulose and salts such as sodium CMC); or alginates. Materialssuitable for the first dressing wicking layer 176 and the seconddressing wicking layer 180 may include, without limitation, any materialhaving a grain structure capable of wicking fluid as described herein,such as, for example, LIBELTEX TDL2, 80 gsm, or similar materials, whichmay be non-woven.

The fluid management assembly 144 may be manufactured as a pre-laminatedstructure, or supplied as individual layers of material that can bestacked upon one another as described above. Individual layers of thefluid management assembly 144 may be bonded or otherwise secured to oneanother without adversely affecting fluid management by, for example,utilizing a solvent or non-solvent adhesive, or by thermal welding.Further, the fluid management assembly 144 may be coupled to the borderof the base layer 132 in any suitable manner, such as, for example, by aweld or an adhesive. The border, being free of the apertures 160 asdescribed herein, may provide a flexible barrier between the fluidmanagement assembly 144 and the tissue site 104 for enhancing comfort.

The addition of the anti-microbial layer 190 may reduce the probabilityof excessive bacterial growth within the dressing 124 to permit thedressing 124 to remain in place for an extended period. Theanti-microbial layer 190 may be, for example, an additional layerincluded as a part of the fluid management assembly 144, or a coating ofan anti-microbial agent disposed in any suitable location within thedressing 124. The anti-microbial layer 190 may be comprised of elementalsilver or a similar compound, for example. In some embodiments, theanti-microbial agent may be formulated in any suitable manner andassociated with other components of the dressing 124.

The dressing 124 may be modified in various embodiments to suit aparticular application. In some embodiments, the absorbent layer 184 maybe omitted from the fluid management assembly 144, which may bebeneficial, but not required, for communicating fluid exterior to oraway from the dressing 124 and the tissue site 104 for offsite or remotestorage. In such an embodiment, the first dressing wicking layer 176 andthe second dressing wicking layer 180 may wick or draw fluid away fromthe tissue site 104 for transport to a location exterior to the dressing124. Further, the configuration of the first dressing wicking layer 176and the second dressing wicking layer 180 described herein maypreference fluid away from the tissue site 104 and prevent the fluidfrom returning to the tissue site 104 prior to removal of the fluid fromthe dressing 124, for example, by the application of negative pressure.The wicking layer enclosure 188 may enhance this ability to preferencefluid away from the tissue site 104 and to prevent the fluid fromreturning to the tissue site 104.

The dressing 124 may be further modified in various embodiments that maybe suitable for some applications that communicate fluid from the tissuesite 104 exterior to the dressing 124. For example, in some embodiments,the first dressing wicking layer 176 or the second dressing wickinglayer 180 may be omitted along with the absorbent layer 184 and the baselayer 132. In such an embodiment, the dressing 124 may comprise thesealing member 140 and one of the first dressing wicking layer 176 orthe second dressing wicking layer 180 for disposing in the sealed space174 between the sealing member 140 and the tissue site 104. Further, insome embodiments, the fluid management assembly 144 may be omitted fromthe dressing 124, and a dressing manifold (not shown) may be positionedin the enclosure 172 in place of the fluid management assembly 144. Thedressing manifold may be configured as a layer and may be comprised ofany material suitable for removing fluids from a tissue site through aplurality of pores, pathways, or flow channels as described herein, suchas, without limitation, a foam, a woven material, a cast silicone, apolyurethane material, or any of the materials recited for the interfacemanifold 120. Further, in some embodiments, the dressing 124 may bemodified by omitting the base layer 132 and replacing the fluidmanagement assembly 144 with the above-described dressing manifold. Insuch an embodiment, the dressing 124 may comprise the sealing member 140and the dressing manifold for disposing in the sealed space 174 betweenthe sealing member 140 and the tissue site 104. Further, in someembodiments, the absorbent layer 184 may be omitted and replaced withthe dressing manifold such that the dressing manifold is positionedbetween the first dressing wicking layer 176 and the second dressingwicking layer 180.

A dressing interface, such as the conduit interface 148 may bepositioned proximate to a cover and in fluid communication with thesealed space 174 provided by the dressing 124. For example, the conduitinterface 148 may be in fluid communication with the dressing 124through an aperture in the sealing member 140. The conduit interface 148may provide negative pressure from the negative-pressure source 128 tothe dressing 124. The conduit interface 148 may also be adapted to bepositioned in fluid communication with the interface manifold 120.

The conduit interface 148 may comprise a medical-grade, soft polymer orother pliable material. As non-limiting examples, the conduit interface148 may be formed from polyurethane, polyethylene, polyvinyl chloride(PVC), fluorosilicone, or ethylene-propylene. In some illustrative,non-limiting embodiments, the conduit interface 148 may be molded fromDEHP-free PVC. The conduit interface 148 may be formed in any suitablemanner such as by molding, casting, machining, or extruding. Further,the conduit interface 148 may be formed as an integral unit or asindividual components and may be coupled to the dressing 124 by, forexample, adhesive or welding.

In some embodiments, the conduit interface 148 may be formed of anabsorbent material having absorbent and evaporative properties. Theabsorbent material may be vapor permeable and liquid impermeable,thereby being configured to permit vapor to be absorbed into andevaporated from the material through permeation while inhibitingpermeation of liquids. The absorbent material may be, for example, ahydrophilic polymer such as a hydrophilic polyurethane. Although theterm hydrophilic polymer may be used in the illustrative embodimentsthat follow, any absorbent material having the properties describedherein may be suitable for use in the system 102. Further, the absorbentmaterial or hydrophilic polymer may be suitable for use in variouscomponents of the system 102 as described herein.

The use of such a hydrophilic polymer for the conduit interface 148 maypermit liquids in the conduit interface 148 to evaporate, or otherwisedissipate, during operation. For example, the hydrophilic polymer mayallow the liquid to permeate or pass through the conduit interface 148as vapor, in a gaseous phase, and evaporate into the atmosphere externalto the conduit interface 148. Such liquids may be, for example,condensate or other liquids. Condensate may form, for example, as aresult of a decrease in temperature within the conduit interface 148, orother components of the system 102, relative to the temperature at thetissue site 104. Removal or dissipation of liquids from the conduitinterface 148 may increase visual appeal and prevent odor. Further, suchremoval of liquids may also increase efficiency and reliability byreducing blockages and other interference with the components of thesystem 102.

The conduit interface 148 may carry the odor filter 194 adapted tosubstantially preclude the passage of odors from the tissue site 104 outof the sealed space 174. Further, the conduit interface 148 may carrythe first hydrophobic filter 195 adapted to substantially preclude thepassage of liquids through the first hydrophobic filter 195. The odorfilter 194 and the first hydrophobic filter 195 may be disposed in theconduit interface 148 or other suitable location such that fluidcommunication between the negative-pressure source 128 and the dressing124 is provided through the odor filter 194 and the first hydrophobicfilter 195. In some embodiments, the odor filter 194 and the firsthydrophobic filter 195 may be secured within the conduit interface 148in a suitable manner, such as by adhesive or welding. In otherembodiments, the odor filter 194 or the first hydrophobic filter 195 maybe omitted, or positioned proximate to an exit location in the system102 or the dressing 124 that is in fluid communication with theatmosphere, the negative-pressure source 128, or the optional therapyunit.

The odor filter 194 may be comprised of a carbon material in the form ofa layer or particulate. For example, the odor filter 194 may comprise awoven carbon cloth filter such as those manufactured by ChemvironCarbon, Ltd. of Lancashire, United Kingdom. The first hydrophobic filter195 may be comprised of a material that is liquid impermeable and vaporpermeable. For example, the first hydrophobic filter 195 may comprise amaterial manufactured under the designation MMT-314 by W.L. Gore &Associates, Inc. of Newark, Del., United States, or similar materials.The first hydrophobic filter 195 may be provided in the form of amembrane or layer.

The liquid trap 192 is representative of a container, canister, pouch,or other storage component, which can be used to manage exudates andother fluids withdrawn from a tissue site. In many environments, a rigidcontainer may be preferred or required for collecting, storing, anddisposing of fluids. In other environments, fluids may be properlydisposed of without rigid container storage, and a re-usable containercould reduce waste and costs associated with negative-pressure therapy.

Similar to the conduit interface 148, the liquid trap 192, and othercomponents of the system 102, may also be formed of an absorbentmaterial or a hydrophilic polymer. The absorptive and evaporativeproperties of the hydrophilic polymer may also facilitate removal anddissipation of liquids residing in the liquid trap 192, and othercomponents of the system 102, by evaporation. Such evaporation may leavebehind a substantially solid or gel-like waste. The substantially solidor gel-like waste may be cheaper to dispose than liquids, providing acost savings for operation of the system 102. The hydrophilic polymermay be used for other components in the system 102 where the managementof liquids is beneficial.

In some embodiments, the absorbent material or hydrophilic polymer mayhave an absorbent capacity in a saturated state that is substantiallyequivalent to the mass of the hydrophilic polymer in an unsaturatedstate. The hydrophilic polymer may be fully saturated with vapor in thesaturated state and substantially free of vapor in the unsaturatedstate. In both the saturated state and the unsaturated state, thehydrophilic polymer may retain substantially the same physical,mechanical, and structural properties. For example, the hydrophilicpolymer may have a hardness in the unsaturated state that issubstantially the same as a hardness of the hydrophilic polymer in thesaturated state. The hydrophilic polymer and the components of thesystem 102 incorporating the hydrophilic polymer may also have a sizethat is substantially the same in both the unsaturated state and thesaturated state. Further, the hydrophilic polymer may remain dry, coolto the touch, and pneumatically sealed in the saturated state and theunsaturated state. The hydrophilic polymer may also remain substantiallythe same color in the saturated state and the unsaturated state. In thismanner, this hydrophilic polymer may retain sufficient strength andother physical properties to remain suitable for use in the system 102.An example of such a hydrophilic polymer is offered under the trade nameTechophilic HP-93A-100, available from The Lubrizol Corporation ofWickliffe, Ohio, United States. Techophilic HP-93A-100 is an absorbenthydrophilic thermoplastic polyurethane capable of absorbing 100% of theunsaturated mass of the polyurethane in water and having a durometer orShore Hardness of about 83 Shore A.

The conduit 196 may have the internal lumen 197 and may be fluidlycoupled between the negative-pressure source 128 and the dressing 124.The internal lumen 197 may have an internal diameter between about 0.5millimeters to about 3.0 millimeters. In some embodiments, the internaldiameter of the internal lumen 197 may be between about 1 millimeter toabout 2 millimeters. The conduit interface 148 may be coupled in fluidcommunication with the dressing 124 and adapted to connect between theconduit 196 and the dressing 124 for providing fluid communication withthe negative-pressure source 128. The conduit interface 148 may befluidly coupled to the conduit 196 in a suitable manner, such as, forexample, by an adhesive, solvent or non-solvent bonding, welding, orinterference fit. An aperture in the sealing member 140 may providefluid communication between the dressing 124 and the conduit interface148. For example, the conduit interface 148 may be in fluidcommunication with the enclosure 172 or the sealed space 174 through theaperture in the sealing member 140. In some embodiments, the conduit 196may be inserted into the dressing 124 through the aperture in thesealing member 140 to provide fluid communication with thenegative-pressure source 128 without use of the conduit interface 148.The negative-pressure source 128 may also be directly coupled in fluidcommunication with the dressing 124 or the sealing member 140 withoutuse of the conduit 196. In some embodiments, the conduit 196 may be, forexample, a flexible polymer tube. A distal end of the conduit 196 mayinclude a coupling 198 for attachment to the negative-pressure source128.

The conduit 196 may have the secondary hydrophobic filter 199 disposedin the internal lumen 197 such that fluid communication between thenegative-pressure source 128 and the dressing 124 is provided throughthe secondary hydrophobic filter 199. The secondary hydrophobic filter199 may be, for example, a porous, sintered polymer cylinder sized tofit the dimensions of the internal lumen 197 to substantially precludeliquid from bypassing the cylinder. The secondary hydrophobic filter 199may also be treated with an absorbent material adapted to swell whenbrought into contact with liquid to block the flow of the liquid. Thesecondary hydrophobic filter 199 may be positioned at any locationwithin the internal lumen 197. However, positioning the secondaryhydrophobic filter 199 within the internal lumen 197 closer toward thenegative-pressure source 128, rather than the dressing 124, may allow auser to detect the presence of liquid in the internal lumen 197.

In some embodiments, the conduit 196 and the coupling 198 may be formedof an absorbent material or a hydrophilic polymer as described above forthe conduit interface 148. In this manner, the conduit 196 and thecoupling 198 may permit liquids in the conduit 196 and the coupling 198to evaporate, or otherwise dissipate, as described above for the conduitinterface 148. The conduit 196 and the coupling 198 may be, for example,molded from the hydrophilic polymer separately, as individualcomponents, or together as an integral component. Further, a wall of theconduit 196 defining the internal lumen 197 may be extruded from thehydrophilic polymer. The conduit 196 may be less than about 1 meter inlength, but may have any length to suit a particular application.

FIG. 2 is a plan view of the base layer 132 of the dressing 124 of FIG.1, illustrating additional details that may be associated with someembodiments. The base layer 132 may have a periphery 152 surrounding acentral portion 156, and the plurality of apertures 160 are disposedthrough the periphery 152 and the central portion 156. The base layer132 may also have corners 158 and edges 159. The corners 158 and theedges 159 may be part of the periphery 152. One of the edges 159 maymeet another of the edges 159 to define one of the corners 158. Further,the base layer 132 may have a border 161 substantially surrounding thecentral portion 156 and positioned between the central portion 156 andthe periphery 152. In some embodiments, the border 161 may be free ofthe apertures 160. In some embodiments, the base layer 132 may beadapted to cover the interface manifold 120 or the apposition layer 146and tissue surrounding the tissue site 104 such that the central portion156 of the base layer 132 is positioned adjacent to or proximate to theinterface manifold 120 or the apposition layer 146, and the periphery152 of the base layer 132 is positioned adjacent to or proximate to thetissue surface 105 surrounding the tissue site 104. In such embodiments,the periphery 152 of the base layer 132 may surround the interfacemanifold 120 or the apposition layer 146. Further, the apertures 160 inthe base layer 132 may be in fluid communication with the interfacemanifold 120 and the tissue surface 105 surrounding the tissue site 104.

The apertures 160 in the base layer 132 may have a variety of shapes,such as, circles, squares, stars, ovals, polygons, slits, complexcurves, rectilinear shapes, triangles, or other shapes. The apertures160 may be formed by cutting (such as laser cutting), by application oflocal RF energy, punching, or other suitable techniques for forming anopening. Each of the apertures 160 of the plurality of apertures 160 maybe substantially circular in shape, having a diameter and an area. Thediameter of each of the apertures 160 may define the area of each of theapertures 160. For example, the area of one of the apertures 160 may bedefined by multiplying the square of half the diameter of the aperture160 by the value 3.14. Thus, the following equation may define the areaof one of the apertures 160: Area=3.14*(diameter/2)̂2.

The area of the apertures 160 described in the illustrative embodimentsherein may be substantially similar to the area in other embodiments(not shown) for the apertures 160 that may have non-circular shapes. Thediameter of each of the apertures 160 may be substantially the same, oreach of the diameters may vary depending, for example, on the positionof the aperture 160 in the base layer 132. For example, the diameter ofthe apertures 160 in the periphery 152 of the base layer 132 may belarger than the diameter of the apertures 160 in the central portion 156of the base layer 132. Further, the diameter of each of the apertures160 may be between about 1 millimeter to about 50 millimeters. In someembodiments, the diameter of each of the apertures 160 may be betweenabout 1 millimeter to about 20 millimeters. The apertures 160 may have auniform pattern or may be randomly distributed on the base layer 132.The size and configuration of the apertures 160 may be designed tocontrol the adherence of the dressing 124 to the epidermis 106 asdescribed below.

In some embodiments, the apertures 160 positioned in the periphery 152may be apertures 160 a, the apertures 160 positioned at the corners 158of the periphery 152 may be apertures 160 b, and the apertures 160positioned in the central portion 156 may be apertures 160 c. In someembodiments, the apertures 160 a may have an area greater than theapertures 160 b. Further, the apertures 160 b may have an area greaterthan the apertures 160 c. The dimensions of the base layer 132 may beincreased or decreased, for example, substantially in proportion to oneanother to suit a particular application.

The apertures 160 a may have a diameter between about 9.8 millimeters toabout 10.2 millimeters. The apertures 160 b may have a diameter betweenabout 7.75 millimeters to about 8.75 millimeters. The apertures 160 cmay have a diameter between about 1.8 millimeters to about 2.2millimeters. The diameter of each of the apertures 160 a may beseparated from one another by a distance A between about 2.8 millimetersto about 3.2 millimeters. Further, the diameter of at least one of theapertures 160 a may be separated from the diameter of at least one ofthe apertures 160 b by the distance A. The diameter of each of theapertures 160 b may also be separated from one another by the distanceA. A center of one of the apertures 160 c may be separated from a centerof another of the apertures 160 c in a first direction by a distance Bbetween about 2.8 millimeters to about 3.2 millimeters. In a seconddirection transverse to the first direction, the center of one of theapertures 160 c may be separated from the center of another of theapertures 160 c by a distance C between about 2.8 millimeters to about3.2 millimeters. The distance B and the distance C may be increased forthe apertures 160 c in the central portion 156 being positionedproximate to or at the border 161 compared to the apertures 160 cpositioned away from the border 161.

The central portion 156 of the base layer 132 may be substantiallysquare with each side of the central portion 156 having a length Dbetween about 100 millimeters to about 108 millimeters. In someembodiments, the length D may be between about 106 millimeters to about108 millimeters. The border 161 of the base layer 132 may have a width Ebetween about 4 millimeters to about 11 millimeters and maysubstantially surround the central portion 156 and the apertures 160 cin the central portion 156. In some embodiments, the width E may bebetween about 9 millimeters to about 10 millimeters. The periphery 152of the base layer 132 may have a width F between about 25 millimeters toabout 35 millimeters and may substantially surround the border 161 andthe central portion 156. In some embodiments, the width F may be betweenabout 26 millimeters to about 28 millimeters. Further, the periphery 152may have a substantially square exterior with each side of the exteriorhaving a length G between about 154 millimeters to about 200millimeters. In some embodiments, the length G may be between about 176millimeters to about 184 millimeters. Although the central portion 156,the border 161, and the periphery 152 of the base layer 132 are depictedas having a substantially square shape, these and other components ofthe base layer 132 may have any shape to suit a particular application.Further, the dimensions of the base layer 132 as described herein may beincreased or decreased, for example, substantially in proportion to oneanother to suit a particular application. The use of the dimensions inthe proportions described above may enhance the cosmetic appearance of atissue site. For example, these proportions may provide a surface areafor the base layer 132, regardless of shape, that is sufficiently smoothto enhance the movement and proliferation of epithelial cells at thetissue site 104, and reduce the likelihood of granulation tissuein-growth into the dressing 124.

The base layer 132 may be a soft, pliable material suitable forproviding a fluid seal with the tissue site 104 as described herein. Forexample, the base layer 132 may comprise a silicone gel, a softsilicone, hydrocolloid, hydrogel, polyurethane gel, polyolefin gel,hydrogenated styrenic copolymer gel, a foamed gel, a soft closed cellfoam such as polyurethanes and polyolefins coated with an adhesive asdescribed below, polyurethane, polyolefin, or hydrogenated styreniccopolymers. The base layer 132 may have a thickness between about 500microns (μm) and about 1000 microns (μm). In some embodiments, the baselayer 132 may have a stiffness between about 5 Shore 00 and about 80Shore 00. Further, in some embodiments, the base layer 132 may becomprised of hydrophobic or hydrophilic materials.

In some embodiments (not shown), the base layer 132 may be ahydrophobic-coated material. For example, the base layer 132 may beformed by coating a spaced material, such as, for example, woven,nonwoven, molded, or extruded mesh with a hydrophobic material. Thehydrophobic material for the coating may be a soft silicone, forexample. In this manner, the adhesive layer 136 may extend throughopenings in the spaced material analogous to the apertures 160.

FIG. 3 is an exploded view of the dressing 124 of FIG. 1, illustratingadditional details that may be associated with some embodiments. Arelease liner 162 may be attached to or positioned adjacent to the baselayer 132 to protect the adhesive layer 136 prior to application of thedressing 124 to the tissue site 104. The fluid management assembly 144may be disposed over the base layer 132. In some embodiments, the fluidmanagement assembly 144 may be disposed over the central portion 156 sothat the apertures 160 c are in fluid communication with the fluidmanagement assembly 144. Preferably, the fluid management assembly 144may be bounded by the border 161 inboard of the periphery 152 of thebase layer 132. The adhesive layer 136 may be disposed over theperiphery 152. In some embodiments, the adhesive layer 136 may be a ringsurrounding the fluid management assembly 144. The adhesive layer 136may be bounded by the edges 159 of the base layer 132 and the border161. The sealing member 140 may be disposed over the adhesive layer 136and the fluid management assembly 144. The sealing member 140 can becoupled to the adhesive layer 136. The sealing member 140 may include anaperture 170 formed near a center of the sealing member 140.

Prior to application of the dressing 124 to the tissue site 104, thebase layer 132 may be positioned between the sealing member 140 and therelease liner 162. Removal of the release liner 162 may expose the baselayer 132 and the adhesive layer 136 for application of the dressing 124to the tissue site 104. The release liner 162 may also provide stiffnessto assist with, for example, deployment of the dressing 124. The releaseliner 162 may be, for example, a casting paper, a film, or polyethylene.Further, the release liner 162 may be a polyester material such aspolyethylene terephthalate (PET), or similar polar semi-crystallinepolymer. The use of a polar semi-crystalline polymer for the releaseliner 162 may substantially preclude wrinkling or other deformation ofthe dressing 124. For example, the polar semi-crystalline polymer may behighly orientated and resistant to softening, swelling, or otherdeformation that may occur when brought into contact with components ofthe dressing 124, or when subjected to temperature or environmentalvariations, or sterilization. Further, a release agent may be disposedon a side of the release liner 162 that is configured to contact thebase layer 132. For example, the release agent may be a silicone coatingand may have a release factor suitable to facilitate removal of therelease liner 162 by hand and without damaging or deforming the dressing124. In some embodiments, the release agent may be fluorosilicone. Inother embodiments, the release liner 162 may be uncoated or otherwiseused without a release agent.

A periphery of the sealing member 140 may be positioned proximate to theperiphery 152 of the base layer 132 such that a central portion of thesealing member 140 and the central portion 156 of the base layer 132define the enclosure 172. The adhesive layer 136 may be positioned atleast between the periphery of the sealing member 140 and the periphery152 of the base layer 132. In some embodiments, a portion of theperiphery of the sealing member 140 may extend beyond the periphery 152of the base layer 132. In other embodiments, the periphery of thesealing member 140 may be positioned in contact with the tissue surface105 surrounding the tissue site 104 to provide the sealed space 174without the base layer 132. Thus, the adhesive layer 136 may also bepositioned at least between the periphery of the sealing member 140 andthe tissue surface 105 surrounding the tissue site 104. The adhesivelayer 136 may be disposed on a surface of the sealing member 140 adaptedto face the tissue site 104 and the base layer 132.

In some embodiments, the adhesive layer 136 may be a layer havingsubstantially the same shape as the periphery 152 of the base layer 132.The adhesive layer 136 may be exposed to at least the apertures 160 b inat least the periphery 152 of the base layer 132. The adhesive layer 136may be positioned adjacent to, or positioned in fluid communicationwith, at least the apertures 160 b in at least the periphery 152 of thebase layer 132.

FIG. 4 is a detail view of a portion of the dressing 124 of FIG. 1,illustrating additional details that may be associated with someembodiments. The adhesive layer 136 may be exposed to or in fluidcommunication with the tissue surface 105 surrounding the tissue site104 through at least the apertures 160 b in the base layer 132. Theadhesive layer 136 may extend, deform, or be pressed through at leastthe plurality of apertures 160 b to contact the tissue surface 105 ofthe epidermis 106 for securing the dressing 124 to, for example, thetissue surface 105 surrounding the tissue site 104. At least theapertures 160 b may provide sufficient contact of the adhesive layer 136to the tissue surface 105 of the epidermis 106 to secure the dressing124 about the tissue site 104. However, the configuration of at leastthe apertures 160 b and the adhesive layer 136 may permit release andrepositioning of the dressing 124 about the tissue site 104.

In some embodiments, the apertures 160 b at the corners 158 of theperiphery 152 may be smaller than the apertures 160 a in other portionsof the periphery 152. For a given geometry of the corners 158, thesmaller size of the apertures 160 b compared to the apertures 160 a mayenhance or increase the surface area of the adhesive layer 136 exposedto the apertures 160 b and to tissue through the apertures 160 b at thecorners 158. The size and number of the apertures 160 b in the corners158 may be adjusted as necessary, depending on the chosen geometry ofthe corners 158, to enhance or increase the exposed surface area of theadhesive layer 136 as described herein.

Similar to the apertures 160 b in the corners 158, any of the apertures160 may be adjusted in size and number to increase the surface area ofthe adhesive layer 136 exposed to or in fluid communication with theapertures 160 for a particular application or geometry of the base layer132. For example, in some embodiments (not shown) the apertures 160 b,or apertures of another size, may be positioned in the periphery 152 andat the border 161. Similarly, the apertures 160 b, or apertures ofanother size, may be positioned as described herein in other locationsof the base layer 132 that may have a complex geometry or shape.

Factors that may be utilized to control the adhesion strength of thedressing 124 may include the diameter, area, and number of the apertures160 in the base layer 132, the thickness of the base layer 132, thethickness and amount of the adhesive layer 136, and the tackiness of theadhesive layer 136. An increase in the amount of the adhesive layer 136extending through the apertures 160 may correspond to an increase in theadhesion strength of the dressing 124. A decrease in the thickness ofthe base layer 132 may correspond to an increase in the amount ofadhesive layer 136 extending through the apertures 160. Thus, thediameter, area, and configuration of the apertures 160, the thickness ofthe base layer 132, and the amount and tackiness of the adhesiveutilized may be varied to provide a desired adhesion strength for thedressing 124.

In some embodiments, the tackiness of the adhesive layer 136 may vary indifferent locations of the base layer 132. For example, in locations ofthe base layer 132 where the apertures 160 are comparatively large, suchas the apertures 160 a, the adhesive layer 136 may have a lowertackiness than other locations of the base layer 132 where the apertures160 are smaller, such as the apertures 160 b and 160 c. In this manner,locations of the base layer 132 having larger apertures 160 and a lowertackiness of the adhesive layer 136 may have an adhesion strengthcomparable to locations having smaller apertures 160 and a highertackiness of the adhesive layer 136.

For low-acuity tissue sites, i.e., tissue sites that do not producelarge amounts of fluids, a storage container, such as the liquid trap192 may provide more capacity than is needed. In some cases, a patientwith a low acuity tissue site may be mobile. To increase a patient'smobility, some dressings include an absorbent component, such as thefluid management assembly 144, to store liquid produced by the tissuesite during therapy. By including an absorbent component in thedressing, the dressing is able to provide a sealed space for therapywithout requiring a patient to carry a secondary storage device. Suchdressings are a useful tool for the provision of negative-pressuretherapy.

Dressings for low-acuity tissue sites may often be what is considered apeel-and-place dressing. A peel-and-place dressing can be a dressingthat is manufactured to include a plurality of components, permitting auser to simply expose an adhesive portion of the dressing and apply thedressing over the tissue site. Such peel-and-place dressings are oftensized to provide coverage of a variety of tissue sites.

For some ambulatory patients, the tissue site, while low-acuity, maynonetheless benefit from the application of a closing force or anapposition force to encourage closure of the tissue site. A closingforce may be a force that is substantially parallel to the tissuesurface 105 and urges opposing sides of a tissue site toward each otherto close an opening of the tissue site. Closure of an opening may helpmaintain a healing environment for internal structures of a tissue site,as well as inhibit entry of bacteria or other harmful substances intothe tissue site. For example, a linear tissue site, such as a surgicalincision, may be a low-acuity tissue site; however, a surgical incisionmay be prone to opening during movement. As a result, an ambulatorypatient may benefit from additional closing forces, forces generallyparallel to the tissue surface 105 that urge an opening to close,encouraging the surgical incision to remain closed. However, manydevices used to provide a closing force are not suitable for use with apeel and place dressing. For example, the device used to provide aclosing force may be bulky, causing the peel-and-place dressing to beunable to seal around the device. Other devices may need additionalcomponents to prevent further trauma to a tissue site. The additionalcomponents may prevent the peel-and-place dressing from forming a sealaround the tissue site, or may inhibit the transmission of negativepressure to the tissue site. Some peel-and-place devices overcome theseissues by providing a peel-and-place dressing that includes a closingdevice. Such devices provide both dressing liquid storage and a closingforce; however, they may not be customizable for different wounds,preventing dynamic placement of the device.

The system 102 having the dressing 124 can provide a peel-and-placedressing having a customizable closing device for dynamic application ofa closing force to a tissue site. For example, the system 102 mayinclude the apposition layer 146. The apposition layer 146 may becustomized to selectively apply a closing or apposition force to atissue site. The dressing 124 may also supply negative pressure andstore liquid produced by the tissue site in the dressing. The appositionlayer 146 may also be sizeable to provide apposition forces to anirregularly shaped tissue site, or to a discontinuous tissue site. Theapposition layer 146 may also be customizable to provide appositionforces to a non-linear tissue site, such as a curved incision.

FIG. 5 is a plan view, illustrating additional details that may beassociated with some embodiments of the apposition layer 146. A sheet147 may be disposed on a surface of the apposition layer 146. The sheet147 may be positioned on a surface of the apposition layer 146 intendedto contact the interface manifold 120 or the tissue surface 105surrounding the tissue site 104. The sheet 147 can also encapsulate theapposition layer 146. For example, the sheet 147 may surround allsurfaces of the apposition layer 146. For example, the sheet 147 maycomprise a continuous sheet of material, the sheet 147 can be wrappedaround the apposition layer 146 and coupled to itself, for example, byadhering, welding, bonding, or otherwise securing, to encapsulate theapposition layer 146. In other embodiments, the sheet 147 may comprisean first layer or upper layer and a second layer or lower layer. Thefirst layer can be disposed over the apposition layer 146 and the secondlayer can be disposed under the apposition layer 146. The first layerand the second layer can be coupled to each other. In some embodiments,the sheet 147 may be wrapped around the apposition layer 146 withoutotherwise securing it to itself, allowing friction following theapplication of negative pressure to hold the sheet 147 in position. Inother embodiments, the sheet 147 may be cut to an approximate size of asurface of the apposition layer 146. The sheet 147 may be coupled to thesurface of the apposition layer 146 to secure the sheet 147 to theapposition layer 146. For example, the sheet 147 may be welded or bondedto the surface of the apposition layer 146, such as with an acrylicadhesive.

The sheet 147 may have at least one perforation and, preferably, aplurality of perforations 149. For example, the first layer may have atleast one perforation and the second layer may have at least oneperforation. Each of the perforations 149 can have an effective diameterof about 2 mm or less. An effective diameter of a non-circular area maybe defined as a diameter of a circular area having the same surface areaas the non-circular area. The perforations 149 may have a pitch of about3 mm. Pitch describes a spacing between objects having translationalsymmetry. The perforations 149 may have a pitch between adjacentperforations 149 in orthogonal directions. The pitch of the perforations149 may be parallel to edges of the sheet 147. In some embodiments,adjacent rows of perforations 149 may be offset. For example, a firstrow of perforations 151 may have a pitch of 3 mm parallel to an edge ofthe sheet 147. A second row of perforations 153 adjacent to the firstrow of perforations 149 may be offset so that a center of eachperforation 149 is equidistant from the centers of adjacent perforations149 in the adjacent rows. In this manner, the perforations 149 may beregularly spaced across the sheet 147. In other embodiments, the pitchbetween adjacent perforations 149 may not be regularly repeating, maynot be parallel to edges of the sheet 147, and may not be continuousacross the sheet 147.

The sheet 147 may be formed from silicone having a coat weight betweenabout 100 gsm and about 200 gsm. In other embodiments, the sheet 147 maybe formed from a hydrogel that has been cross-linked sufficient toprevent absorption, dissociation, mobility, and breakdown or apolyurethane having a thickness of about 50 microns to about 200microns. In some embodiments, the sheet 147 may be coated onto anon-woven scrim layer. The non-woven scrim layer may have a coatingweight of about 25 gsm to about 100 gsm, corresponding to a thickness ofabout 25 microns to 100 microns. The scrim layer may be formed frompolyurethane, polyamide, polyester, or cellulosic material. The hydrogelof the sheet 147 may be coated on one or both sides of the scrim layer.In other embodiments, the sheet 147 may be coated onto a mesh scrimlayer or formed without the use of a scrim. The sheet 147 may beprovided in sheets having a length of about 200 mm. The sheet 147 may beadherent, permitting the sheet 147 to adhere to the apposition layer 146and the interface manifold 120. If the sheet 147 is adherent, the sheet147 may have a peel force between about 0.5N/25 mm and about 6N/25 mm.The peel forces is the measure of the average force required to part twomaterials bonded by an adhesive.

The sheet 147 may mimic the base layer 132 in operation and benefits tothe healing of a tissue site. For example, the sheet 147 may aid in scarreduction of an incisional tissue site. The sheet 147 may preventingrowth into layers or bodies disposed over the sheet 147, such as theapposition layer 146. The sheet 147 may also act as a comfort layer,aiding in pain free application of therapy.

The apposition layer 146 may include a plurality of holes 602 orperforations extending through the apposition layer 146 to form walls608 extending through the apposition layer 146. In some embodiments, thewalls 608 may be generally parallel to a thickness of the appositionlayer 146. In other embodiments, the walls 608 may be generallyperpendicular to a surface of the apposition layer 146. In someembodiments, the holes 602 may have an ellipsoid shape as shown.

FIG. 6A is a plan view, illustrating additional details that may beassociated with some embodiments of the apposition layer 146 disposedover the tissue site 104 so that the apposition layer 146 may beproximate to the tissue surface 105. The sheet 147 is not shown to aidin illustration of features of the apposition layer 146. The appositionlayer 146 may be formed from a foam. For example, cellular foam,open-cell foam, reticulated foam, or porous tissue collections, may beused to form the apposition layer 146. In some embodiments, theapposition layer 146 may be formed of GranuFoam®, grey foam, orZotefoam. Grey foam may be a polyester polyurethane foam having about 60pores per inch (ppi). Zotefoam may be a closed-cell crosslinkedpolyolefin foam. The apposition layer 146 can also be formed from apolyvinyl alcohol (PVA) foam or a 3D foam. In one non-limiting example,the apposition layer 146 may be an open-cell, reticulated polyurethanefoam such as GranuFoam® dressing available from Kinetic Concepts, Inc.of San Antonio, Tex.; in other embodiments, the apposition layer 146 maybe an open-cell, reticulated polyurethane foam such as a VeraFlo® foam,also available from Kinetic Concepts, Inc., of San Antonio, Tex.

In some embodiments, the apposition layer 146 may be formed from a foamthat is mechanically or chemically compressed to increase the density ofthe foam at ambient pressure. A foam that is mechanically or chemicallycompressed may be referred to as a compressed foam or a felted foam. Acompressed foam may be characterized by a firmness factor (FF) that canbe defined as a ratio of the density of a foam in a compressed state tothe density of the same foam in an uncompressed state. For example, afirmness factor (FF) of 5 may refer to a compressed foam having adensity that is five times greater than a density of the same foam in anuncompressed state. Mechanically or chemically compressing a foam mayreduce a thickness of the foam at ambient pressure when compared to thesame foam that has not been compressed. Reducing a thickness of a foamby mechanical or chemical compression may increase a density of thefoam, which may increase the firmness factor (FF) of the foam.Increasing the firmness factor (FF) of a foam may increase a stiffnessof the foam in a direction that is parallel to a thickness of the foam.For example, increasing a firmness factor (FF) of the apposition layer146 may increase a stiffness of the apposition layer 146 in a directionthat is parallel to the thickness 126 of the apposition layer 146. Insome embodiments, the apposition layer 146 may have a thickness of about6 mm. In other embodiments, the thickness 126 may be between about 5 mmand about 10 mm. In some embodiments, a compressed foam may be acompressed GranuFoam®. GranuFoam® may have a density of about 0.03 gramsper centimeter³ (g/cm³) in its uncompressed state. If the GranuFoam® iscompressed to have a firmness factor (FF) of 5, the GranuFoam® may becompressed until the density of the GranuFoam® is about 0.15 g/cm³.VeraFlo® foam may also be compressed to form a compressed foam having afirmness factor (FF) up to 5.

The firmness factor (FF) may also be used to compare compressed foammaterials with non-foam materials. For example, a Supracor® material mayhave a firmness factor (FF) that allows Supracor® to be compared tocompressed foams. In some embodiments, the firmness factor (FF) for anon-foam material may represent that the non-foam material has astiffness that is equivalent to a stiffness of a compressed foam havingthe same firmness factor. For example, if the apposition layer 146 isformed from Supracor®, the apposition layer 146 may have a stiffnessthat is about the same as the stiffness of a compressed GranuFoam®material having a firmness factor (FF) of 3. Generally, a materialhaving a firmness factor (FF) of about 1 may have a stiffness of about 5kPa. A stiffness of 5 kPa requires the application of about 5 kPa tocompress the material to 50% of its original thickness. A materialhaving a firmness factor (FF) of about 3 corresponds to the applicationof about 15 kPa to compress the material to 50% of its originalthickness, that is, a stiffness of about 15 kPa. The apposition layer146 may have a stiffness between about 10 kPa to about 20 kPa.

Generally, if a compressed foam is subjected to negative pressure, thecompressed foam exhibits less deformation than a similar uncompressedfoam. If the apposition layer 146 is formed of a compressed foam, thethickness 126 of the apposition layer 146 may deform less than if theapposition layer 146 is formed of a comparable uncompressed foam. Thedecrease in deformation may be caused by the increased stiffness asreflected by the firmness factor (FF). If subjected to the stress ofnegative pressure, the apposition layer 146 formed of compressed foammay flatten less than the apposition layer 146 that is formed fromuncompressed foam. Consequently, when negative pressure is applied tothe apposition layer 146, the stiffness of the apposition layer 146 inthe direction parallel to the thickness 126 of the apposition layer 146allows the apposition layer 146 to be more compliant or compressible inother directions, e.g., a direction parallel to the tissue surface 105or in a direction perpendicular to a lesion, incision, or opening of thetissue site 104. The foam material used to form a compressed foam may beeither hydrophobic or hydrophilic. The pore size of a foam material mayvary according to needs of the apposition layer 146 and the amount ofcompression of the foam. For example, in some embodiments, anuncompressed foam may have pore sizes in a range of about 400 microns toabout 600 microns. If the same foam is compressed, the pore sizes may besmaller than when the foam is in its uncompressed state. In someembodiments, the apposition layer 146 may have a width 610. The width610 may be between about 15 mm and about 40 mm.

The apposition layer 146 may cover a lesion, incision, or opening in thetissue surface 105 of the tissue site 104. In some embodiments, theapposition layer 146 may have a first orientation line 627 and a secondorientation line 629 that is perpendicular to the first orientation line627. The first orientation line 627 may be parallel to an edge 632 ofthe apposition layer 146 and the second orientation line 629 may beparallel to an edge 634 of the apposition layer 146. In someembodiments, the first orientation line 627 and the second orientationline 629 may be used to refer to the desired directions of contractionfor the apposition layer 146. For example, if the first orientation line627 is oriented parallel to the lesion, incision, or opening, thedesired direction of contraction may be parallel to the secondorientation line 629 and perpendicular to the first orientation line627. Generally, the apposition layer 146 may be placed at the tissuesite 104 so that the first orientation line 627 is parallel to thelesion, incision, or opening and may cover portions of the tissuesurface 105 on one or more sides of the lesion, incision, or opening. Insome embodiments, the first orientation line 627 may be coincident withthe lesion, incision, or opening. The apposition layer 146 may includethe plurality of holes 602 or perforations extending through theapposition layer 146. In some embodiments, the walls 608 of the holes602 may extend through the apposition layer 146 parallel to thethickness 126 of the apposition layer 146. In some embodiments, theholes 602 may have an ovoid shape as shown.

Referring more specifically to FIG. 7, a single hole 602 having an ovoidshape is shown. The hole 602 may include a center 636, a perimeter 638,and a perforation shape factor (PSF). For reference, the hole 602 mayhave an X-axis 642 extending through the center 636 parallel to thefirst orientation line 627, and a Y-axis 640 extending through thecenter 636 parallel to the second orientation line 629. In someembodiments, the perforation shape factor (PSF) of the hole 602 may bedefined as a ratio of a line segment 644 on the Y-axis 640 extendingfrom the center 636 to the perimeter 638 of the hole 602, to a linesegment 646 on the X-axis 642 extending from the center 636 to theperimeter 638 of the hole 602. If a length of the line segment 644 is2.5 mm and the length of the line segment 646 is 2.5 mm, the perforationshape factor (PSF) would be 2.5/2.5 or about 1.

Referring to FIG. 8, if the hole 602 is rotated relative to the firstorientation line 627 and the second orientation line 629 so that a majoraxis of the hole 628 is parallel to the second orientation line 629 anda minor axis of the hole 602 is parallel to the first orientation line627, the perforation shape factor (PSF) may change. For example, theperforation shape factor (PSF) is now the ratio of a line segment 660 onthe Y-axis 640 extending from the center 636 to the perimeter 638 of thehole 628, to a line segment 662 on the X-axis 642 extending from thecenter 636 to the perimeter 638 of the hole 628. If a length of the linesegment 660 is 5 mm and the length of the line segment 662 is 2.5 mm,the perforation shape factor (PSF) would be 5/2.5 or about 2.

Referring to FIG. 9, if the hole 602 is rotated relative to the firstorientation line 627 and the second orientation line 629 so that a majoraxis of the hole 602 is parallel to the first orientation line 627 and aminor axis of the hole 602 is parallel to the second orientation line629, the perforation shape factor (PSF) may change. For example, theperforation shape factor (PSF) is now the ratio of a line segment 664 onthe Y-axis 640 extending from the center 636 to the perimeter 638 of thehole 628, to a line segment 666 on the X-axis 642 extending from thecenter 636 to the perimeter 638 of the hole 602. If a length of the linesegment 664 is 2.5 mm and the length of the line segment 666 is 5 mm,the perforation shape factor (PSF) would be 2.5/5 or about ½.

Referring to FIG. 6B, a portion of the apposition layer 146 of FIG. 6Ais shown. The apposition layer 146 may include the plurality of holes602 aligned in a pattern of parallel rows. The pattern of parallel rowsmay include a first row 648 of the holes 602, a second row 650 of theholes 602, and a third row 652 of the holes 602. The X-axis 642 of FIGS.8, 9, and 10 of each hole 602 may be parallel to the first orientationline 627 of FIG. 7B. The centers 636 of the holes 602 in adjacent rows,for example, the first row 648 and the second row 650, may becharacterized by being offset from the second orientation line 629 alongthe first orientation line 627. In some embodiments, a line connectingthe centers of adjacent rows may form a strut angle (SA) with the firstorientation line 627. For example, a first hole 602A in the first row648 may have a center 637A, and a second hole 602B in the second row 650may have a center 637B. A strut line 654 may connect the center 637Awith the center 637B. The strut line 654 may form an angle 656 with thefirst orientation line 627. The angle 656 may be the strut angle (SA) ofthe apposition layer 146. In some embodiments, the strut angle (SA) maybe less than about 60°. In other embodiments, the strut angle (SA) maybe between about 30° and about 70° relative to the first orientationline 627. As described above, if negative pressure is applied to theapposition layer 146, the apposition layer 146 may be more compliant orcompressible in a direction perpendicular to the first orientation line627. By increasing the compressibility of the apposition layer 146 in adirection perpendicular to the first orientation line 627, theapposition layer 146 may collapse to apply the closing force 631 to thelesion, incision, or opening of the tissue site 104, as described inmore detail herein.

In some embodiments, the centers 636 of the holes 602 in alternatingrows, for example, the center 637A of the first hole 602A in the firstrow 648 and a center 636C of a hole 602C in the third row 652, may bespaced from each other parallel to the second orientation line 629 by alength 658. In some embodiments, the length 658 may be greater than aneffective diameter of the hole 602. If the centers 636 of holes 602 inalternating rows are separated by the length 658, the walls 608 parallelto the first orientation line 627 may be considered continuous.Generally, the walls 608 may be continuous if the walls 608 do not haveany discontinuities or breaks between holes 602.

Regardless of the shape of the holes 602, the holes 602 in theapposition layer 146 may leave void spaces in the apposition layer 146and on the surface of the apposition layer 146 so that only the walls608 of the apposition layer 146 remain with a surface available tocontact the surface of the tissue site 104. It may be desirable tominimize the walls 608 so that the holes 602 may collapse, causing theapposition layer 146 to collapse the closing force 631 in a directionperpendicular to the first orientation line 627. However, it may also bedesirable not to minimize the walls 608 so much that the appositionlayer 146 becomes too fragile for sustaining the application of anegative pressure. The void space percentage (VS) of the holes 602 maybe equal to the percentage of the volume or surface area of the voidspaces created by the holes 602 to the total volume or surface area ofthe apposition layer 146. In some embodiments, the void space percentage(VS) may be between about 40% and about 60%. In other embodiments, thevoid space percentage (VS) may be about 56%.

In some embodiments, an effective diameter of the holes 602 may beselected to permit flow of particulates through the holes 602. In someembodiments, each hole 602 may have an effective diameter of about 7 mm.In other embodiments, each hole 602 may have an effective diameterbetween about 2.5 mm and about 20 mm.

FIG. 6C is a plan view of the apposition layer 146 in a second position,illustrating additional details that may be associated with someembodiments. The holes 602 may form a pattern depending on the geometryof the holes 602 and the alignment of the holes 602 between adjacent andalternating rows in the apposition layer 146 with respect to the firstorientation line 627. If the apposition layer 146 is subjected tonegative pressure, the holes 602 of the apposition layer 146 maycollapse, causing the apposition layer 146 to collapse along the secondorientation line 629 perpendicular to the first orientation line 627. Ifthe apposition layer 146 is positioned on a tissue surface of the tissuesite 104 so that the first orientation line 627 coincides with thelesion, incision, or opening, the apposition layer 146 may generate aclosing force 631 along the second orientation line 629 such that thetissue surface is contracted in the same direction to facilitate closureof the lesion, incision, or opening. The closing force 631 may beoptimized by adjusting the factors described above as set forth in Table1 below. In some embodiments, the holes 602 may be ovular, have a strutangle (SA) of approximately 47°, a void space percentage (VS) of about56%, a firmness factor (FF) of 5, a perforation shape factor (PSF) of 1,and an effective diameter of about 7 mm (where the major axis is about 8mm and the minor axis is about 5 mm). If the apposition layer 146 issubjected to a negative pressure of about −125 mm Hg, the appositionlayer 146 may assert the closing force 631 of approximately 13.5 N.

In some embodiments, the apposition layer 146 and the sheet 147 may bedisposed within a subcutaneous tissue site. If disposed in asubcutaneous tissue site, the apposition layer 146 and the sheet 147 mayapproximate the subcutaneous tissue.

A closing force, such as the closing force 631, generated by aapposition layer, such as the apposition layer 146, may be related to acompressive force generated by applying negative pressure at a therapypressure to a sealed therapeutic environment. For example, the closingforce 631 may be proportional to a product of a therapy pressure (TP) inthe sealed therapeutic environment or a sealed space 174, thecompressibility factor (CF) of the apposition layer 146, and a surfacearea (A) of the apposition layer 146. The relationship is expressed asfollows:

Closing force α(TP*CF*A)

In some embodiments, the therapy pressure TP is measured in N/m², thecompressibility factor (CF) is dimensionless, the area (A) is measuredin m², and the closing force is measured in Newtons (N). Thecompressibility factor (CF) resulting from the application of negativepressure to a contracting layer may be, for example, a dimensionlessnumber that is proportional to the product of the void space percentage(VS) of a contracting layer, the firmness factor (FF) of the contractinglayer, the strut angle (SA) of the holes in the contracting layer, andthe perforation shape factor (PSF) of the holes in the contractinglayer. The relationship is expressed as follows:

Compressibility Factor(CF)α(VS*FF*sin(SA)*PSF)

Based on the above formulas, contracting layers formed from differentmaterials with holes of different shapes were manufactured and tested todetermine the closing force of the contracting layers. For eachcontracting layer, the therapy pressure TP was about −125 mmHg and thedimensions of the contracting layer were about 200 mm by about 53 mm sothat the surface area (A) of the contracting layer was about 106 cm² or0.0106 m². Based on the two equations described above, the closing forcefor a Supracor® contracting layer 114 having a firmness factor (FF) of 3was about 13.3 where the Supracor® contracting layer 114 had hexagonalholes 702 with a distance between opposite vertices of 5 mm, aperforation shape factor (PSF) of 1.07, a strut angle (SA) ofapproximately 66°, and a void space percentage (VS) of about 55%. Asimilarly dimensioned GranuFoam® contracting layer 114 generated theclosing force 631 of about 9.1 Newtons (N).

TABLE 1 Major Hole diam. Closing Material VS FF SA Shape PSF (mm) forceGranuFoam ® 56 5 47 Ovular 1 10 13.5 Supracor ® 55 3 66 Hexagon   1.1  513.3 GranuFoam ® 40 5 63 Triangle   1.1 10 12.2 GranuFoam ® 54 5 37Circular 1  5 11.9 GranuFoam ® 52 5 37 Circular 1 20 10.3 Grey Foam N/A5 N/A Horizontal N/A N/A 9.2 stripes GranuFoam ® 55 5 66 Hexagon   1.1 5 9.1 GranuFoam ® N/A 5 N/A Horizontal N/A N/A 8.8 stripes Zotefoam 523 37 Circular 1 10 8.4 GranuFoam ® 52 5 37 Circular 1 10 8.0 GranuFoam ®52 5 64 Circular 1 10 7.7 GranuFoam ® 56 5 66 Hexagon   1.1 10 7.5 GreyFoam N/A 3 N/A Horizontal N/A N/A 7.2 stripes Zotefoam 52 3 52 Circular1 20 6.8 GranuFoam ® N/A 3 N/A Horizontal N/A N/A 6.6 StripingGranuFoam ® 52 5 52 Circular 1 20 6.5 GranuFoam ® N/A 5 N/A Vertical N/AN/A 6.1 Stripes GranuFoam ® N/A 1 N/A None N/A N/A 5.9 GranuFoam ® N/A 3N/A Vertical N/A N/A 5.6 stripes GranuFoam ® 52 1 37 None 1 10 5.5

FIG. 10 is a perspective view of the apposition layer 146 and thedressing 124, illustrating additional details associated with someembodiments. In operation, the apposition layer 146 covered by the sheet147 may be positioned over the tissue site 104. The sheet 147 contactsthe tissue surface 105 and adheres the apposition layer 146 to thetissue surface 105, holding the apposition layer 146 on the tissuesurface 105. Preferably, the apposition layer 146 is aligned with thetissue site 104 so that a length of the apposition layer 146 isgenerally parallel an opening of the tissue site 104. The appositionlayer 146 may be bisected by the opening of the tissue site 104 so thatthe apposition layer 146 contacts a portion of the tissue surface 105 onopposite sides of the opening of the tissue site 104.

The dressing 124 can be positioned over the apposition layer and thesheet 147. Preferably, the dressing 124 is aligned with the appositionlayer 146 so that the central portion 156 of the base layer 132 is overthe apposition layer 146.

FIG. 11 is a perspective view of the apposition layer 146 and thedressing 124 adhered to the tissue surface 105, illustrating additionaldetails that may be associated with some embodiments. Some components ofthe dressing 124 are not shown in FIG. 11 to aid in illustration of thedescribed features. While components may not be shown, the componentscan be included. As shown in FIG. 11, the apposition layer 146 isbordered by the border 161 of the base layer 132. In other embodiments,the apposition layer 146 may extend into the border 161 or further.

FIG. 12 is a perspective view of the apposition layer 146 and thedressing 124 during negative-pressure therapy, illustrating additionaldetails that may be associated with some embodiments. As shown, theapposition layer 146 generates the closing force 631 urging the openingof the tissue site 104 closed. The apposition layer 146 can generate theclosing force 631 while also distributing fluids from the tissue site104 into the fluid management assembly 144.

FIG. 13A is a perspective section view of another apposition layer 1646,illustrating additional details that may be associated with someembodiments. The apposition layer 1646 may be similar to and operate asdescribed above with respect to the apposition layer 146. For example,the apposition layer 1646 includes a plurality of holes 1602. Theplurality of holes 1602 may be similar to and operate as described abovewith respect to the plurality of holes 602 of the apposition layer 146.The apposition layer 1646 may also have a thickness 1626. The thickness1626 may be similar to and operate as described above with respect tothe thickness 126 of the apposition layer 146. The apposition layer 1646may also include a plurality of walls 1608. The plurality of walls 1608may be similar to and operate as described above with respect to theplurality of walls 608 of the apposition layer 146. In some embodiments,the apposition layer 1646 may include a film (not shown) encapsulatingthe apposition layer 1646. The film may be similar to and operate asdescribed above with respect to the sheet 147 of the apposition layer146.

The apposition layer 1646 may have a first end 1648 and a second end1650 opposite the first end 1648. In some embodiments, the first end1648 and the second end 1650 may be a width of the apposition layer1646. The apposition layer 1646 may include a first side 1652 extendingbetween the first end 1648 and the second end 1650. The apposition layer1646 also includes a second side 1654 opposite the first side 1652. Theapposition layer may also include a top surface 1656 and a bottomsurface 1658 opposite the top surface 1656. Edges are formed at theintersection of the top surface 1656 with the first side 1652 and thesecond side 1654. Similarly, edges are formed at the intersection of thebottom surface 1658 and the first side 1652 and the second side 1654.The edge between the top surface 1656 and the first side 1652 may beremoved to form a first angled surface 1620. The first angled surface1620 may be a beveled or chamfered surface, forming an angle 1660 withthe top surface 1656. In some embodiments the angle 1660 may be about 45degrees. In other embodiments, the angle 1660 may be between about 20degrees and about 75 degrees. Similarly, the edge between the topsurface 1656 and the second side 1654 may be removed to form a secondangled surface 1622; the edge between the bottom surface 1658 and thefirst side 1652 may be removed to form a third angled surface 1624; andthe edge between the bottom surface 1658 and the second side 1654 may beremoved to form a fourth angled surface 1628. Each of the second angledsurface 1622, the third angled surface 1624, and the fourth angledsurface 1628 may form an angle with the respective top surface 1656 andthe bottom surface 1658 that is similar to the angle 1660. In someembodiments, the first angled surface 1620, the second angled surface1622, the third angled surface 1624, and the fourth angled surface 1628may include the holes 1602.

FIG. 13B is a cross-sectional view of the apposition layer 1646 of FIG.13A taken along line 13B-13B, illustrating additional details that maybe associated with some embodiments. In at least some embodiments, asealing member 1640 may be positioned over the apposition layer 1646,creating a sealed space that includes the apposition layer 1646. Thesealing member 1640 may be similar to and operate as described abovewith respect to the sealing member 140 of FIG. 1. If placed over theapposition layer 1646, the sealing member 1640 may be in contact withthe top surface 1656 and contoured to contact the first angled surface1620 and the second angled surface 1622 of the apposition layer 1646.Gaps may be formed between the third angled surface 1624 and tissueadjacent the tissue site and the fourth angled surface 1628 and tissueadjacent the adjacent tissue. As illustrated in FIG. 10B, the appositionlayer 1646 is in a first position. In the first position, the bottomsurface 1658 may contact a surface of a tissue site, for example,undamaged tissue adjacent the tissue site. In the first position, asealed space formed by the sealing member 1640 that includes theapposition layer 1646 may be at an ambient pressure.

FIG. 13C is a cross-sectional view of the apposition layer 1646 of FIG.13A in a second position, illustrating additional details that may beassociated with some embodiments. If fluid is drawn from the sealedspaced formed by the sealing member 1640, generating a negativepressure, the apposition layer 1646 may be drawn down into the secondposition or compressed position. In the second position, any gaps formedbetween the third angled surface 1624 and the tissue adjacent the tissuesite or between the fourth angled surface 1628 and the tissue adjacentthe tissue site may close. The third angled surface 1624 and the fourthangled surface 1628 may contact the tissue adjacent the tissue site.Closing of the gap between third angled surface 1624 and the fourthangled surface 1628 may draw the first angled surface 1620 and thesecond angled surface 1622 downward and inward. The angle 1660 of thefirst angled surface 1620 and the second angled surface 1622 maytransition the sealing member 1640 in a smooth manner, minimizing anylocal disturbance of the tissue adhered to the sealing member 1640. Insome embodiments, the gap between the first angled surface 1620 and thesecond angled surface 1622 may collapse under partial application ofnegative pressure, for example, under a negative pressure less thanabout 120 mm Hg. Collapse under partial application of negative pressuremay decrease the angle of adherence, mitigating the application of loadand reducing the amount of skin reddening or blister formation that mayoccur from the apposition layer 1646. Furthermore, the first angledsurface 1620, the second angled surface 1622 may decrease the totalvolume of the sealing space formed by the sealing member 1640, requiringremoval of less fluid to generate a therapeutic negative pressure than asimilar apposition layer having sides formed by right angles.

The apposition layer 1646 transitioning from the first position to thesecond position may generate an apposition force at the tissue site. Forexample, the apposition layer 1646 may generate an apposition force 1662from the first side 1652 toward the second side 1654 and from the secondside 1654 toward the first side 1652. The apposition layer 1646 can bepositioned over a tissue site, such as an incision where the first side1652 is on a first side of the incision and the second side 1654 is on asecond side of the incision, so that the apposition layer 1646 straddlesthe incision. The apposition force 1662 can draw the opposing sides ofthe incision toward each other, encouraging the incision to close.

FIG. 14 is a perspective view of another embodiment of an appositionlayer 1746, illustrating additional details that may be associated withsome embodiments. The apposition layers described herein can be sized.For example, the apposition layer 1746 can be provided in strips and cutto size to a desired size to cover a tissue site. The apposition layer1746 may be similar to and operate as described above with respect tothe apposition layer 146. Some tissue sites may be irregularly shaped.For example, a tissue site 1704 may be formed from two incisions, ahorizontal incision 1705 and a vertical incision 1703. In someembodiments, the vertical incision 1703 may intersect the horizontalincision 1705 near a center of the horizontal incision 1705. Theintersection of the horizontal incision 1705 and the vertical incision1703 may cause the tissue site 1704 to be shaped like a “T.” Theapposition layer 1746 can be formed to have a shape matching the shapeof the tissue site. For example, the apposition layer 1746 may comprisestrips of the apposition layer 1746 that can be formed to match thetissue site, for example by cutting. In the illustrated embodiment, theapposition layer 1746 may include a first apposition layer 1745 and asecond apposition layer 1747. The first apposition layer 1745 may be cutto a length of the vertical incision 1703, and the second appositionlayer 1747 may be cut to a length of the horizontal incision 1705. Thefirst apposition layer 1745 can be placed over the vertical incision1703 and the second apposition layer 1747 can be positioned over thehorizontal incision 1705. The first apposition layer 1745 and the secondapposition layer 1747 may include a sheet (not shown) similar to thesheet 147 of the apposition layer 146. After placement over the tissuesite 104, the first apposition layer 1745 and the second appositionlayer 1747 may be covered by an appropriately sized dressing, such asthe dressing 124. The dressing 124 may be sized so that the border 161of the base layer 132 surrounds the apposition layer 1746. Duringoperation, a negative-pressure source may be coupled to the dressing 124and operated to draw down the dressing 124 and the apposition layer1746. The first apposition layer 1745 may develop an apposition forceperpendicular to the vertical incision 1703, and the second appositionlayer 1747 may develop an apposition force perpendicular to thehorizontal incision 1705, urging the tissue site 1704 closed asdescribed above with respect to the apposition layer 146.

In other embodiments, the tissue site 1704 may be discontinuous. Forexample, the vertical incision 1703 may not intersect the horizontalincision 1705. The first apposition layer 1745 may be placed over thevertical incision 1703 and the second apposition layer 1747 can beplaced over the horizontal incision 1705. The first apposition layer1745 may not abut the second apposition layer 1747, providing an areauncovered by the apposition layer 1746. In this manner, the appositionlayer 1746 may provide apposition forces where needed, and provide noapposition forces where not needed.

FIG. 15 is a perspective view of another embodiment of an appositionlayer 1846, illustrating additional details that may be associated withsome embodiments. The apposition layers described herein can becustomized. For example, the apposition layer 1846 can be provided instrips and cut to provide a curvature or an angled portion to cover asimilarly shaped tissue site. The apposition layer 1846 may be similarto and operate as described above with respect to the apposition layer146. Some tissue sites may be irregularly shaped. For example, a tissuesite 1804 may be curved. The apposition layer 1846 can be formed to havea shape matching the shape of the tissue site. For example, theapposition layer 1846 may comprise strips of the apposition layer 1846that can be formed to match the tissue site, for example by cutting. Inthe illustrated embodiment, the apposition layer 1846 may be curved tomatch the radius of curvature of the tissue site 1804. For example, theapposition layer 1846 may have a plurality cuts 1870 formed along afirst side of the apposition layer 1846. The cuts 1870 may segment theapposition layer 1846, permitting the apposition layer 1846 to expandalong the side having the cuts 1870. The expansion of the side of theapposition layer 1846 having the cuts 1870 causes the opposite side tocontract, curing the apposition layer 1846. In some embodiments, thecuts 1870 permit the apposition layer 1846 to match the curvature of thetissue site 1804. The apposition layer 1847 may also be cut to a lengthof the tissue site 1804. The apposition layer 1846 may include a sheet(not shown) similar to the sheet 147 of the apposition layer 146. Afterplacement over the tissue site 104, the apposition layer 1846 may becovered by an appropriately sized dressing, such as the dressing 124.The dressing 124 may be sized so that the border 161 of the base layer132 surrounds the apposition layer 1846. During operation, anegative-pressure source may be coupled to the dressing 124 and operatedto draw down the dressing 124 and the apposition layer 1846. The firstapposition layer 1845 may develop an apposition force perpendicular tothe tissue site 1804, urging the tissue site 1804 closed as describedabove with respect to the apposition layer 146.

The systems, apparatuses, and methods described herein may providesignificant advantages. For example, the apposition layers describedherein can permit apposition forces to be applied with a peel-and-placenegative-pressure dressing. The addition of apposition forces by theapposition layer does not require modifications to peel-and-placedressings, allowing additional therapies to be performed withoutincreasing the complexity of application of the therapy device. Theapposition layers described herein further permit customization that canallow an apposition layer to be customized to a particular tissue site,such as a contoured tissue site, or even a discontinuous tissue site.Furthermore, the apposition layers described herein permit a clinicianto selectively place apposition force within a negative pressuredressing. Selective placement may allow areas that may be damaged byapposition forces to still receive negative pressure therapy. Theapposition layers can also manifold pressure and fluid into theabsorbent structure of a dressing. The apposition layers describedherein can also maintain a position while a dressing is being placedover the apposition layer through the use of the sheet to envelop theapposition layer. The sheet, often formed of silicone, may also helpreduce scar formation and can be particularly advantageous in a surgicaldressing used for aesthetic reasons.

While shown in a few illustrative embodiments, a person having ordinaryskill in the art will recognize that the systems, apparatuses, andmethods described herein are susceptible to various changes andmodifications. Moreover, descriptions of various alternatives usingterms such as “or” do not require mutual exclusivity unless clearlyrequired by the context, and the indefinite articles “a” or “an” do notlimit the subject to a single instance unless clearly required by thecontext. Components may be also be combined or eliminated in variousconfigurations for purposes of sale, manufacture, assembly, or use.

The appended claims set forth novel and inventive aspects of the subjectmatter described above, but the claims may also encompass additionalsubject matter not specifically recited in detail. For example, certainfeatures, elements, or aspects may be omitted from the claims if notnecessary to distinguish the novel and inventive features from what isalready known to a person having ordinary skill in the art. Features,elements, and aspects described or illustrated in the context of someexample embodiments may also be omitted or combined with features,elements, and aspects of other example embodiments. Features, elements,and aspects described herein may also be combined or replaced byalternative features serving the same, equivalent, or similar purposewithout departing from the scope of the invention defined by theappended claims.

1. A system for closing an opening through a surface of a tissue site,the system comprising: an apposition layer adapted to be positioned overthe opening, the apposition layer comprising: a material having afirmness factor, and a plurality of holes extending through theapposition layer, the holes forming a void space and having aperforation shape factor and a strut angle configured to collapse theapposition layer in a first direction relative to a second direction; afirst layer adapted to be positioned below the apposition layer, thefirst layer having at least one perforation; a second layer adapted tobe positioned above the apposition layer, the second layer having atleast one perforation; a dressing adapted to cover the apposition layerto form a sealed space; and a negative-pressure source adapted to befluidly coupled to the sealed space to provide negative pressure to thesealed space; wherein the apposition layer generates a closing force inthe first direction that is substantially parallel to the surface of thetissue site to close the opening in response to application of thenegative pressure.
 2. The system of claim 1, wherein the first layer andthe second layer each comprise a silicone adhesive.
 3. The system ofclaim 1, wherein the first layer and the second layer each comprise asilicone adhesive having a coating weight between about 100 gsm andabout 200 gsm.
 4. The system of claim 1, wherein the first layer and thesecond layer each comprise a polyurethane material.
 5. The system ofclaim 1, wherein the first layer and the second layer each comprise ahydrogel.
 6. The system of claim 1, wherein the first layer and thesecond layer comprise a single, continuous sheet of material.
 7. Thesystem of claim 1, wherein the at least one perforation of the firstlayer comprises a plurality of perforations.
 8. The system of claim 7,wherein the at least one perforation of the second layer comprises aplurality of perforations.
 9. The system of claim 1, wherein the atleast one perforation of the second layer comprises a plurality ofperforations.
 10. The system of claim 1, wherein the plurality of holeshave an average effective diameter of about 5 mm.
 11. The system ofclaim 1, wherein the plurality of holes are formed in two or moreparallel rows.
 12. The system of claim 1, wherein the strut angle isabout 90 degrees.
 13. The system of claim 1, wherein the strut angle isless than about 90 degrees.
 14. The system of claim 1, wherein theperforation shape factor of each hole is less than about
 1. 15. Thesystem of claim 1, wherein a thickness of the apposition layer is about15 mm.
 16. The system of claim 1, wherein the firmness factor is about5.
 17. The system of claim 1, wherein the firmness factor is about 3.18. The system of claim 1, wherein a shape of each hole of the pluralityof holes is elliptical.
 19. The system of claim 1, wherein theapposition layer comprises a felted foam.
 20. The system of claim 1,wherein the dressing comprises: a base layer having a plurality ofapertures extending through the base layer, at least a portion of theplurality of apertures configured to transmit fluid across the baselayer; a fluid management assembly positioned over the base layer, thefluid management assembly comprising: a first wicking layer; anabsorbent disposed over the first wicking layer, and a second wickinglayer disposed over the absorbent and having a periphery coupled to aperiphery of the first wicking layer to enclose the absorbent; a sealingmember disposed over the fluid management assembly; and an adhesivelayer positioned between a periphery of the base layer and the sealingmember, the adhesive layer coupling the base layer to the sealing memberto enclose the fluid management assembly.
 21. The system of claim 20,wherein the plurality of apertures in the base layer comprise: a firstgroup of apertures disposed in a center portion of the base layer andhaving a first diameter; a second group of apertures disposed in aperimeter portion of the base layer and having a second diameter, thefirst group of apertures and the second group of apertures separated bya border; and the second group of apertures having an average diameterthat is larger than the average diameter of the first group ofapertures.
 22. An apparatus for closing an opening through a surface ofa tissue site, the apparatus comprising: an contracting layer adapted tobe positioned over the opening, the contracting layer comprising: amaterial having a firmness factor, and a plurality of holes extendingthrough the contracting layer, the holes forming a void space and havinga perforation shape factor and a strut angle configured to collapse thecontracting layer in a first direction relative to a second direction; alower layer adapted to be positioned below the contracting layer, thelower layer having at least one perforation; and an upper layer adaptedto be positioned above the contracting layer, the upper layer having atleast one perforation; wherein the contracting layer generates a closingforce substantially parallel to the surface of the tissue site to closethe opening in response to application of a negative pressure.
 23. Theapparatus of claim 22, wherein the lower layer and the upper layer eachcomprise a silicone adhesive.
 24. The apparatus of claim 22, wherein thelower layer and the upper layer each comprise a silicone adhesive havinga coating weight between about 100 gsm and about 200 gsm.
 25. Theapparatus of claim 22, wherein the lower layer and the upper layer eachcomprise a polyurethane material.
 26. The apparatus of claim 22, whereinthe lower layer and the upper layer each comprise a hydrogel.
 27. Theapparatus of claim 22, wherein the lower layer and the upper layercomprise a single, continuous sheet of material.
 28. The apparatus ofclaim 22, wherein the at least one perforation of the lower layercomprises a plurality of perforations.
 29. The apparatus of claim 28,wherein the at least one perforation of the upper layer comprises aplurality of perforations.
 30. The apparatus of claim 22, wherein the atleast one perforation of the upper layer comprises a plurality ofperforations.
 31. The apparatus of claim 22, wherein the plurality ofholes have an average effective diameter of about 5 mm.
 32. Theapparatus of claim 22, wherein the plurality of holes are formed in twoor more parallel rows.
 33. The apparatus of claim 22, wherein the strutangle is about 90 degrees.
 34. The apparatus of claim 22, wherein thestrut angle is less than about 90 degrees.
 35. The apparatus of claim22, wherein the perforation shape factor of each hole is less thanabout
 1. 36. The apparatus of claim 22, wherein a thickness of thecontracting layer is about 15 mm.
 37. The apparatus of claim 22, whereinthe firmness factor is about
 5. 38. The apparatus of claim 22, whereinthe firmness factor is about
 3. 39. The apparatus of claim 22, wherein ashape of each hole of the plurality of holes is elliptical.
 40. Theapparatus of claim 22, wherein the contracting layer comprises acompressed foam.
 41. The apparatus of claim 22, further comprising adressing configured to form a sealed space over the contracting layer,the dressing comprising: a base layer having a plurality of aperturesextending through the base layer, at least a portion of the plurality ofapertures configured to transmit fluid across the base layer; a fluidmanagement assembly positioned over the base layer, the fluid managementassembly comprising: a first wicking layer; an absorbent disposed overthe first wicking layer, and a second wicking layer disposed over theabsorbent and having a periphery coupled to a periphery of the firstwicking layer to enclose the absorbent; a sealing member disposed overthe fluid management assembly; and an adhesive layer positioned betweena periphery of the base layer and the sealing member, the adhesive layercoupling the base layer to the sealing member to enclose the fluidmanagement assembly.
 42. The apparatus of claim 41, wherein theplurality of apertures in the base layer comprise: a first group ofapertures disposed in a center portion of the base layer and having afirst diameter; a second group of apertures disposed in a perimeterportion of the base layer and having a second diameter, the first groupof apertures and the second group of apertures separated by a border;and the second group of apertures having an average diameter that islarger than the average diameter of the first group of apertures.
 43. Amethod for closing an opening through a surface of a tissue site, themethod comprising: encapsulating an apposition layer in a sheet havingan upper layer above the apposition layer and a lower layer below theapposition layer, the sheet having at least one perforation in the upperlayer and at least one perforation in the lower layer; positioning theapposition layer over the opening, the apposition layer adapted to bepositioned adjacent the opening and formed from a material having afirmness factor and a plurality of holes extending through theapposition layer to form a void space, the holes having a perforationshape factor and a strut angle causing the apposition layer to collapsein a direction substantially perpendicular to the opening; andcollapsing the apposition layer parallel to the surface of the tissuesite to generate a closing force.
 44. The method of claim 43, furthercomprising: positioning a sealing member over the apposition layer;sealing the sealing member to tissue surrounding the tissue site to forma sealed space; and fluidly coupling a negative-pressure source to thesealed space.
 45. The method of claim 44, wherein collapsing theapposition layer comprises: supplying negative pressure to the sealedspace with the negative-pressure source.
 46. The method of claim 45,wherein collapsing the apposition layer comprises: supplying negativepressure to the apposition layer.
 47. The method of claim 45, whereincollapsing the apposition layer comprises: collapsing the appositionlayer in response to a supply of negative pressure; and drawing edges ofthe apposition layer toward a center of the apposition layer in responseto the collapse of the holes of the apposition layer.
 48. (canceled)